Hubby How To: DIY Planter Box


Do you want to grow your own veggies, flowers, or herbs but don’t have the space for a full garden? We’ve designed a beautiful long planter box that works great for decks and small areas. Here are the tools, materials, and how-to to build your own DIY planter box.

Updated 09/26/2023

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There’s not always space to have a massive garden, but you may still want to be growing herbs and veggies or even just flowers. We definitely don’t have flat areas in our yard, but wanted to grow some more of our own food. Growing our own food let’s us spend less at the grocery stores, reduce our plastic consumption, and live in a more sustainable way. And we’re serial DIYers, so we decided to design and build our own DIY wood planter box to put on our deck for growing.

This post gives you the plans and covers the tools, materials, and a step-by-step to build a beautiful wood planter box. We’ll also cover two different ways to assemble the planter box; one with hidden screws on the interior and one with screws on the exterior. Let’s get started!

Tools & Materials For DIY Planter Box

DIY Plans



1” x 3” x 96” Board665
1” x 6” x 96” Board11119
Large Gravel3 cu. ft.2.5 cu. ft.2 cu. ft.
Pea Gravel1.5 cu. ft1 cu. ft.1 cu. ft.
Garden Soil10 cu. ft9 cu. ft.7.5 cu. ft.
Surface Area9.74 M28.77 M27.80 M2
Rubio Hybrid Wood Protector*0.32 L0.29 L0.26 L

* NOTE: Rubio estimates their hybrid wood protector will cover 30 square meters when used for exterior applications. Softer woods like Cedar may absorb more so your usage may vary.

Materiality Considerations For Planter Boxes

Materials and cost will vary depending on how long you want the DIY planter box to be and the wood type you choose. Below are some examples and considerations. Bring the materials list from the DIY plans with you to make sure you get what you need.

Wood Selection

Let’s start with wood selection. After having a good plan, this is the second step to any project and it can make or break a project. The cheapest option is to use Common Boards, which are typically made from soft pine or fir. They don’t generally hold up as well in the long run, but are still usable for outdoor projects if properly finished. However these wouldn’t be a good choice for a planter box since they’ll be in contact with the ground. 

A slight step up is Select Pine. These are generally straighter and prettier than Common Boards, but they still aren’t rot resistant and are likely to fail in a few years.

The best option is to use a naturally rot resistant wood like Cedar. This wood typically costs more than the previous options. However, it looks beautiful when finished and will hold up for years to come. We personally feel this is the best choice and decided to go with this option for our DIY planter boxes.

Hubby Tip: You may be tempted to buy Ground Contact Pressure Treated wood, because it would last the longest. Unfortunately, the same chemicals that make it so rot resistant are also likely to seep into your soil and get absorbed into your plants. You don’t want these chemicals getting into any plants that you intend to eat, so steer clear of those for this project.

Finding Affordable Cedar

Hardwood dealers will usually have better quality boards, but you can often find cedar at big box stores as well. But note, that “premium” cedar boards can be ridiculously expensive at these stores! 

So head over to the decking section. Here you can find cheaper options for cedar boards. These boards are better than the cheap cedar pickets or the unfinished cedar boards, but some of them may be slightly warped. Pay for these slightly nicer boards and spend the time to check each one for straightness and flatness. 

Gravel & Soil

The gravel will go into the bottom of the planter box to help the soil drain. We’ll need a base layer of larger gravel a few inches deep to aid in drainage, then a smaller layer of pea gravel to help keep the soil out of the gravel. If you have landscape fabric, you can throw some of that in there as well. Just make sure the fabric is permeable and allows water to flow through it. Otherwise, you just made a bathtub and likely your plants will die from sitting in water too much.

As for the soil, you will want to fill the planter box up with a rich organic soil blend. Quick tip here, you can save a lot of money and cut down on plastic bag waste by buying your soil in bulk from a local organic recycler. These are companies that convert food and yard waste into compost for resale. Do a quick internet search to see if there is one in your area. If you’re a Kansas City local, we got the raised bed mix from Missouri Organic Recycling.


For screws, you will want to go with something exterior-rated. We used the Deckmate brand screws of our project. Another important thing to look for though are the drive and the threads. I highly recommend getting screws with the Torx Star Drive over the typical Phillips head. The star pattern grips well and I haven’t had one strip out yet. The same can’t be said for Phillips heads.

Wood Finishes

Finally, you’ll need a wood finish for the planter box. We’ve built this planter box multiple times over the years and done it two ways. We’re always learning and we’ve found we have a preferred option.

Oil & Urethane Finish

The first time we built the planter boxes we oiled them with linseed oil and sealed them with a spar urethane. 

If you do decide to oil the wood, then use linseed oil or mineral oil. Be careful though! Boiled linseed oil generally has chemicals added to help it dry faster that could leech into the soil. You’ll want a raw linseed oil or a chemical-free boiled linseed oil (sometimes called Double boiled). Moreover, if you decide to stain the box, then be sure to do your research and find a natural stain. Then consider sealing the boards with nautical polyurethane or “spar urethane”. If you want to paint your boards, then be sure to pick a brand of exterior paint with Low VOC.

The biggest issue we’ve had is that the oil and spar urethane finishes we used have failed to prevent the cedar from graying in some spots and preserved it in others.

Hybrid Wood Protector

Fast forward a few years and we’ve been using Rubio Monocoat on our projects and have absolutely loved the results. When making this planter box again, we decided to use Rubio’s Hybrid Wood Protector, which is an oil-based exterior wood finish. It has a semi-transparent look to it and comes in 22 colors. 

Every color, except the “Pure”, has UV stabilizers to provide color stability against the natural aging of the wood. We used the Teak color which evened out the cedar wood color tones, but kept it relatively the same hue. It’ll stay that color too, instead of graying like our previous finish on the older planter boxes.

It may seem expensive, but it only requires one coat of product, no topcoat to seal it, and the quality is unmatched. Considering the cost of the oil and urethane and spending multiple hours applying, waiting for it to dry, and then applying more, we’ve found the Monocoat approach is our preferred choice. Not to mention that it just looks so much better as well!

Alright! Time to Start!

DIY Planter Box – Step-by-Step How To

Step 1: Get Plans & Materials

While you could just wing-it, we always find it easier to have a set of plans. It helps us easily keep track of dimensions and quantities, so that we don’t have to run to the store five times over the course of the DIY project. We’ve done the hard work for you and made a set of printable DIY Plans for you. This will give you all of the dimensions and quantities you’ll need along with step-by-step assembly instructions!

Included in the DIY plan set, you will find a materials list that breaks down 3 different planter box lengths like the list above. Moreover, it also includes recommended board cut layouts to help you effectively maximize your materials without too much scrap wood leftover. Simply print off this list and circle the column for the design you are going to make. Now you have a handy dandy shopping list to take to your local store.

DIY planter box drawing package sheets laying on workbench

Step 2: Layout The Cuts

Once you have the boards home, lay them out on the workbench and decide what board faces you like the most. The less desirable 1×6’s will be the bottom boards and the 1x3s will be the internal support structure.

Mark up all of the boards and label everything so you can match them back up properly later. If you bought longer boards or are building smaller boxes, try to lay out the cuts so you can wrap the grain around the corners for a beautiful effect. 

To help speed up the layout, you can clamp the boards together and use a large square to mark up multiple boards at once. If you use stop blocks later to ensure everything is consistent, you will have a little wiggle room here. 

Mitered Corners Vs. Butt-Joints

The measurements provided assume that the corners you cut are mitered corners. If you choose to make only straight cuts instead, then you’ll need to remove the material thickness of a board from the length of one board at each corner. 

For example, If you choose to do straight cuts for the siding and want to leave the front and back boards the full length, then you’ll need to shorten the side boards. So rather than being 18” long with mitered corners they would be 18” – 0.75” – 0.75” = 16.5” long with straight-cut corners. Mark up your prints in advance so that you don’t forget this detail later.

Step 3: Cut Boards To Length

Once everything is laid out, start by rough-cutting everything on the miter saw. This gets everything down into its individual pieces and makes the boards easier to manage. Just make sure you cut on the right side of your line. Don’t let your mind go into zombie mode halfway though or you may end up having to shrink your design by an ⅛” and trim everything all over again. 

Line up your miter saw blade with the cut lines being sure you check where the teeth of the blade will remove material. That ⅛” can add up and throw you off when it’s time to assemble.

Step 4: Plane Boards (Optional)

Next, run the boards through the planner real quick to clean up the faces, if needed. 

This step is optional and depends on the quality and thickness of the boards you purchased. The cedar boards we bought were marketed as 5/4, but they were really only a hair over 1” thick. This worked for us because then we could plane down both sides to make them ¾” and ensure they are flat. 

If your boards are already ¾” you can skip this step. If your boards have any significant cup or twist though, it can be tough to recover the boards without losing a lot of material. You can try to use a jointer or planer sled to flatten them out if you have enough thickness that you can salvage it.

Step 5: Cut Mitered Corners For Side Boards

Now for the trickier part, the mitered corners! There are two ways to do this. You can either use a miter saw or a table saw.

Option 1: Miter Saw

This was the method we used the first time we built the planter boxes. Here’s that process: 

  • Start by rotating the miter saw to 45 degrees and lock it in place.
  • Align the board so the edge of the saw blade contacts the upper edge of the board.
  • Clamp the board in place and cut the mitered edge. Be careful when cutting at these angles to keep your hands out of the path of the saw. 
  • Repeat the process to cut the mitered edge on all of the side pieces.

There is enough flex in our miter saw that we can move the angle by hand, so this method isn’t perfect for us. It means that getting crisp miters is very difficult. If you don’t have a table saw, or you have a much nicer miter saw, then that method will still work. 

Option 2: Table Saw (Preferred)

The second time we built this, we wanted to ensure that the corners were nice and tight this time around, and for that, we used a cross-cut sled. The great thing about using a cross-cut sled is you can set up stop blocks. This helps ensure the boards end up being the same length.

Here’s the table saw process:

  • Set the table saw blade to just past 45 degrees so there are no gaps in the outside edge of the miters.
  • Lay the board onto the cross-cut sled and set up a stop block. Double-check you have the correct face up on each board if you are trying to achieve a grain wrap.
    • For these longer boards, set up a stop block on a side support table. Just make sure the stop block is no longer touching the board when you make the cut so it doesn’t cause any binding. The rounded profile we have on our stop block helps prevent that.
  • Cut mitered corner using the cross-cut sled on the table saw
  • Repeat this process for all the side boards.

This process goes real quickly with the stop blocks and the corners turn out much tighter!

Step 6: Glue Up

Once all of the planter box side boards are cut, next it’s time to glue them up. Make sure you are using exterior-rated wood glue to ensure the glue holds up to outdoor weather and is waterproof.

If you intend to simply use screws on the exterior of the planter box, you can technically skip this step. Adding wood glue to hold it together would be a redundancy, but it does help keep the corners tight. It’s up to you. 

Start by evenly coating each face of the joint with glue to ensure there’s good penetration and a strong joint. This is especially important on mitered corners since they are practically end grain. Then fit the boxes together and secure them while drying. 

For mitered boxes like this, we like to use strap clamps or ratchet straps with corner blocks to get good pressure on all of the corners. We 3D printed these corner blocks to convert our ratchet straps and they work pretty well. Run the strap around the perimeter of the box and crank it down tight. Let the glue dry for the time noted on the product, usually set in 30-6- minutes and cured in 24 hours.

Step 7: Cut Interior Support Boards

Now that the boxes are done, we can cut the interior pieces to their final dimensions. You can use the measurement given in the DIY plans. However, we waited to do this step until now, just in case something happened during the box build that would affect the overall dimensions of the pieces. 

If the box is glued together, you can stack all three layers on top of the bottom boards and then use your actual pieces of wood for the interior supports to mark the correct height and width on them directly.This will be much more accurate, account for any previous measuring errors and is super fast as well.

You can use a miter saw to chop them down or a table saw with a stop block again. Repeat until all the interior support boards are the appropriate lengths.

Step 8: Cut Mitered Corner on Top Board

Next, it is time to cut the top board cap with its mitered corners. Double-check your dimensions for the overall length of the box. Just like the side boards, there’s two ways to achieve mitered corners: using a miter saw or a cross-cut sled on a table saw.

Option 1: Miter Saw

  • Use a framing square to mark the cuts for the mitered corners of your top pieces. 
  • Rotate the miter saw back up to its vertical (0 degree) position and then rotate the base to its 45-degree position.
  • Align the blade up with the line on your boards and cut the mitered corners.
  • Repeat for all corners

Option 2: Table Saw (Preferred)

  • Set the table saw blade to just past 45 degrees so there are no gaps in the outside edge of the miters.
  • Place a framing square against the back fence of the cross-cut sled and clamp the board down
  • Cut the board to the 45-degree angle.
    •  Since you can’t set up a good stop block for these, make sure to take extra time to ensure the boards ended up the correct length.
  • Repeat this for all the corners.

Once all the top pieces are cut, glue them with the exterior-rated wood glue and hold them together with strap clamps until dry. 

Step 10: Adding Splines (Optional)

Even as experienced DIYer’s, we still make mistakes. With the latest planter box, we accidentally used the incorrect wood glue. It was interior-rated only and not water-proof. But we couldn’t get the box back apart. So we had to get creative and add something to add strength and hold it together if the glue failed.

We added splines to the corners! A spline is basically a strip of wood inserted into matching grooves along the edges of two boards. These not only look cool, they also greatly add to the strength of a mitered corner. So you can totally add these for fun, even if you used the correct glue.

Make A Spline Jig

To add splines, make a jig that will hold the box at a 45 degree angle and slide along your table saw’s fence. Start by cutting two strips of plywood and then attaching them to a larger piece to create a frame that hugs the fence. If there’s a little bit of play in this fit, add a few strips of tape to fill in the gap. Next, attach two pieces of scrap wood to the plywood at 45-degree angles. Then you’re ready to cut some splines!

Cutting Splines

First, make sure your box will clear the ceiling when on the jig cutting. Ours definitely didn’t, so we moved the table saw outside.

Then set the fence to where you want the spline to fall. We set ours at about 1” in from the edges. Next, run all of the corners through, flip the box over, and run them through again. Nothing to it! It’s always worth it to make a jig.

Glue Splines & Cut Flush

Next, cut some scrap wood pieces down to the right thickness and length to be the spline. This can be the same cedar or you can use another hardwood for contrast and make it an accent piece. Then glue the spline pieces into the grooves you cut on the table saw with the exterior-rated wood glue.

Once the glue dries, come back with a pull saw and chisel to trim them flush. A great tip here is to tape off the teeth on the opposite side of your saw so you don’t accidentally scratch the piece. Beautiful. Tada! Splines added and mitered corners strengthened!

Step 11: Sanding

Next to start the finishing process, sand down all your planter box pieces. We recommend getting yourself a good orbital sander and using the 3M Xtract Sandpaper. This sandpaper is amazing and it makes sanding go soooo much faster. Try it, seriously.

Sand everything from 80 grit down to 180 grit on the exterior faces. The faces inside the box where the gravel and soil can only be sanded with 80 grit if you want as they won’t be exposed.

Don’t Forget To Clean The Wood

After sanding everything, don’t forget to vacuum the dust off the boards and then clean them with mineral spirits. This helps ensure the finish adheres well and evenly to the boards. To help the boards dry faster, we set up a fan and then left them to sit overnight. We want them to be completely dry before we apply our finish.

Step 12: Finishing The Wood

As previously mentioned, you can finish the planter box several different ways. We’ve done two different methods: oil & spar urethane, and a hybrid wood protector. We prefer using Rubio Monocoat’s Hybrid Wood Protector as the previous oil and spar urethane finish has allowed greying of the wood.

The Hybrid Wood Protector product goes on a little differently than their Oil Plus 2C does. After cleaning the wood’s surfaces and letting it dry, start by stirring the oil and then measuring out the amount needed. Since this is being used for a planter box, we added 10% per volume of the hardener to the mix per Rubio’s specifications. So, for 100 mL of product, we would add 10 mL of hardener. Then we mix it up and we are ready to start.

  • Then begin by applying a layer of the Hybrid Wood Protector with a flat brush. 
  • Leave it to react for 10 minutes, before coming back with the same brush to smooth the surface. We’re not applying any new product here. We are just smoothing it out. 
  • Let it sit for another 5 minutes 
  • Then use a rag to buff off the excess product.

All that’s left now is to let it dry. The boards will be ready to handle in about 24 hours, and completely cured after 7 days. We used the Teak color on the cedar and we love how amazing the planter boxes look.

Step 13: Assemble The Planter Box

Once the finish has dried enough for handling, we can go ahead and put the planter box together. This assembly is super simple so the box goes together very quickly. 

Start by screwing together the internal support pieces in a U-shape and then add the crossbeam. After that, there are two ways to assemble the box: screws on the exterior or hidden screws on the inside.

Option 1: Screws On The Exterior of Planter Box

This process uses screws all along the exterior of the box.

  • Start with standing the internal support pieces up on a table upside down.
  • Align the edges of the bottom boards with the support structure and screw everything together.
  • Flip the planter box body over, and it’s time to start putting together the sides if you didn’t glue them together previously.
  • Lay the bottom most piece of front siding against your box frame along with a side piece. 
  • Align the edges of your mitered corners and press them against your upright to keep everything square.
  • Drill a pilot hole for the screw using a countersink drill bit.
    • If you don’t have a countersink drill bit, then compare the head of your screw to your drill bits to find one that’s about the same size. Use that to remove some material around the pilot hole. This will help the screw sink in and be more flush without crushing into the wood and possibly splitting it. This step isn’t normally necessary, but since we are right on the edge of the board, you’ll want to take this precaution.
  • Screw your boards together.
  • Repeat this for the other side piece, and then repeat again for the back piece.
  • Repeat these steps two more times to get all the layers of the planter box.
  • Now screws these boxes into your support frame.
  • Place the Top Board cap on to the box, align the corners, and screw them down.

Option 2: Hidden Screws On Interior of Planter Box (Preferred)

This option only works if you used the exterior-rated wood glue on the mitered corners and have each layer pre-assembled.

  • Lay out the bottom boards and then stack each side layer in desired order
  • Set internal support pieces inside the planter box
  • Drive screws through the sides of the support pieces into the exterior side layers. One screw in every layer and ever support piece is sufficient.
  • Screw a screw into every support piece into the bottom boards as well from the inside of the box.
  • To attach the top board cap, drill angled pilot holes for pocket screws and make recess for the heads to fit into. 
  • Finally, drop the cap on top and attach it with the pocket holes from below.

Step 14: Add Gravel & Soil

All that’s left now is to move the box into place and fill it up with rocks and soil! But first, make sure that your planter’s coating cured fully before you put any soil into them. With Rubio, this is seven days after application. 

Move Before You Fill

I recommend you finalize where you would like to put the planter before you start dumping rocks and soil in it. Because it likely won’t be moving for a while. These planters will weigh a few hundred pounds by the time you’re done.

Also, if you choose to put these on a deck like we did, make sure you are putting them over the main support structure of the decks so their weight is transferred as directly to the columns as possible. 

Add Gravel & Soil

Start with a base layer of larger gravel a few inches deep to aid in drainage. Then a smaller layer of pea gravel to help keep the soil out of the gravel. 

If you have landscape fabric, you can throw some of that in there as well, just make sure the fabric is permeable and allows water to flow through it. 

Then fill the planter box up with a rich organic soil blend.

Step 15: Add Plants & Enjoy!

All that’s left is to add plants, watch them grow, and enjoy! We’ve grown everything from herbs like basil and mint to leafy greens and tomatoes in our DIY planter boxes over the years. It’s amazing what you can grow in a few feet of soil!

More DIY Projects

With your new planter box built, you might be considering doing some more DIY projects or what to plant. Check out more of our DIY projects and gardening/homesteading articles for inspiration!

Let us know how your DIY Planter Box turned out and share your tips in the comments! We love to hear from others and are always looking to improve!

Disclaimer: This post includes affiliate links, and I will earn a commission if you purchase through these links. Please note that I’ve linked to these products purely because I recommend them and they are from companies I trust. There is no additional cost to you.

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